Dithiol-4-imines

3-Dithiol-4-imines (Anhy dr o-4-amino-1,3-dithiolium Hydroxides) (141) 

The cyanomethyl dithio ester (142, R1 = Ph, R2 = H) and an ethereal solution of hydrogen chloride yields the salt 143, R1 = Ph, R2 = R3 = H, X = Cl.96 This hydrochloride (143, R1 = Ph, R2 = H) could not be acylated directly, but the cyanomethyl dithio ester (142, R1 = Ph, R2 = H) with benzoyl or acetyl chloride gave the salts 143, R1 = Ph, R2 = H, R3 = COPh or COMe, which with aqueous sodium hydrogen carbonate gave the red meso-ionic derivatives 141, R1 = Ph, R2 = H, R3 = COPh or COMe.90 96 

Irradiation of a benzene solution of anhydro-4-benzoylamino-2-phenyl-l,3-dithiolium hydroxide (141, R1 = Ph, R2 = H, R3 = COPh) yields the 1,2-dithiole (145, 80%). This photoisomerization has been interpreted as involving the bicyclic intermediate 144.97 

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In the 1,2-dithiole series such imines are readily isolated they can be alkylated or protonated, e.g. (448) (449) (66AHC(7)39). 

The formation of an isothiazole ring from the thiophene system (5) is of interest. Probably ammonia breaks the sulfur-carbonyl bond and then adds to the second carbonyl group, giving an imine (8), which is then oxidized by the hydrogen peroxide. A number of similar rearrangements and interconversions of isothiazole, thiophene, and dithiole systems are known and will be discussed later (Section II,C,3). 

Dithiolanes (1), in contrast to other dithioles, are not planar. In the carboxylic acid (28a) the CSSC dihedral angle is 26.6° (B-61MI43100), leading to a strain of 67 kJ mol-1. These compounds are unstable and the parent may be obtained only in dilute solution. Lipoic acid (29) is more stable, but does polymerize. The instability may account for its particular reactivity (B-61MI43101). l,2-Dithiol-3-ones (3a) and -3-thiones (3b) are very stable, as is evident from their modes of formation. Simple l,2-dithiol-3-imines (3c) are also stable, but some readily interconvert to isothiazoline-3-thiones (30) (Section 4.31.3.2). 

Carbon nucleophiles may react at the sulfur-sulfur bond, or at C-3. Thus Grignard reagents react with monocyclic dithiol-3-ones (3a) and -3-imines (3c) at S-2 (74LA1261,73LA247). The product (84) of reaction of a Grignard reagent with benzo-1,2-dithiol-3-one (77a) (74T4113) could be alternately formed by attack at S-2, at C-3 or at C-5. Phosphonium ylides or other stabilized carbanions react at the 3-position of dithiol-ones... 

The oxime of benzoylacetamide forms 5-phenylisoxazole (152) (58AC(R)577) on treatment with phosphorus pentasulfide, and on further treatment this is converted into 5-phenyl-l,2-dithiole-3-thione (90b). Also, isoxazoljne-3-thiones (153) react with hydrogen sulfide to form mixtures of dithiol-3-imines (3c) and isothiazoline-3-thiones (40) (80CPB487). 

Mixed-ligand diimine dithiolate complexes of Zn(II) were among the first compounds classified as having a LLCT excited state (131). The complexes Zn(phen)(tdt) (41), Zn(bpy)(tdt) (42), and Zn(biq)(tdt) (43), where biq = 2,2 -biquinoline, were reported to have absorption bands at wavelengths of 475 nm (80 M-1 cm-1), 465 nm (65 A/-1 cm-1), and 590 nm (40 M-1 cm-1), respectively. The LLCT transition is attributed to a HOMO that is localized on the dithiolene and a LUMO that is localized on the diimine, with a clear relationship to the MMLL CT transition described for the square-planar M(di-imine)(dithiolate) complexes (M = Ni, Pd, Pt) described in Section II.C. However, the relative orientations of the two planar ligands in the <78 square planar and the dw pseudotetrahedral complexes are quite different, and have a profound influence on the absorption and emission properties. 

Addor s synthesis of the hydrochlorides of the benzoisotrithione imines from benzene-1,2-dithiol and cyanogen chloride has already been discussed in detail (Section III, A, 1, a). 

Dithiol-2-imines, formation in 1,3-anionic cycloaddition reactions of a,/3-unsaturated thiolates 87UK267. 

Amino-l,2-dithiolium salts are obtained from either / -oxocarbox-amides or ) -oxocarbonitriles by reaction with phosphorus penta-sulfide, followed by addition of perchloric acid (Scheme 6). These cations, which may also be considered as iminium salts, are deprotonated to the corresponding l,2-dithiol-3-imine by ammonia. ... 

By contrast, 5-aryl-3-chlorothio(or 3-bromothio)-1,2-dithiolium ions react with primary arylamines to give 5-aryl-l,2-dithiol-3-imines. This difference of behavior is clearly a result of the stabilizing effect of 5-aryl substituents on the 1,2-dithiole ring. 

Methyl iodide also reacts with 1,3-dithiol-2-imines (129) leading to... 

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